1. Field of the Invention
The invention relates to a method for searching an optimum value. Particularly, the invention relates to a method for searching an optimum phase delay value of a memory.
2. Description of Related Art
In recent years, since a double data rate (DDR) synchronous dynamic random access memory (SDRM) has advantages of low power consumption, high durability, and high accessing speed, it is widely used in electronic products such as notebooks, workstations, servers, routers and switches.
In order to stably access the memory, an accessing method thereof is to suitably delay a data queue strobe (DQS) signal, and then latch a data queue (DQ) signal of the memory. Generally, a delay time of the DQS signal is determined by setting a phase delay value, and the delay time can be changed by changing the phase delay value. Moreover, the current delay time of the DQS signal is set according to a predetermined value, and the predetermined value is set according to a data sheet provided by a manufacturer. However, the phase delay value set according to the data sheet provided by the manufacturer cannot be adjusted along with factors such as an environment, a device state or a circuit layout, etc., so that the delay time of the DQS signal is probably not an optimum setting, and therefore an accessing state of the memory is unstable.